Intercomparison of line-parameter spectroscopic databases using downwelling spectral radiance

Abstract

Ground-based Fourier Transform Spectrometer observations in the infrared, acquired during the Italian phase of the EAQUATE campaign, have been considered in this study and compared to calculations. Synthetic spectral radiances have been obtained using the 2000 and 2004 releases and the 2006 upgrade of HITRAN spectral databases. It has been found that synthetic radiance computations fit the data quite well, even though the goodness of the fit depends on the spectral database. Differences in the spectral residual behaviour appear to be mostly localized in the long-wave side of the Earth emission spectrum, i.e. in the spectral region 520-610 cm −1 , which is dominated by the water vapour rotational absorption band. In this range, computation performed with the latest updates provides almost the same results as those of HITRAN2000, while HITRAN2004 shows a mixed behaviour -better than the first two in a large region of the spectral range, but worse at very few specific wave numbers. Overall, HITRAN2006 yields the highest consistency with the observations. No sensitive differences appear at higher wave numbers.

Transmission spectroscopy with the ACE-FTS infrared spectral atlas of Earth: A model validation and feasibility study

“…Moreover, the version of the continuum did not change the model spectrum notably (the H 2 O continuum is especially important in the lower troposphere). Esposito et al [91] noted that "typical differences introduced by the two H 2 O continuum models are of one order of magnitude less than typical differences arising from different line parameters." In conclusion, the choice of spectroscopic input data is not expected to impact the analysis substantially.…”

The Zugspitze radiative closure experiment for quantifying water vapor absorption over the terrestrial and solar infrared – Part 1: Setup, uncertainty analysis, and assessment of far-infrared water vapor continuum

“…Because of the strong absorption, the measured radiance in this spectral region strongly correlates to the temperature of the environment close to the instrument. We use the retrieval scheme developed by Esposito et al (2007) for this kind of boundary layer temperature inversion, which has been successfully utilized by a series of studies Masiello et al, 2012;Liuzzi et al, 2014). A similar approach has been used by Rowe et al (2006) and Rowe and Walden (2009).…”

“…Furthermore, water vapor feedback approximately doubles the response of surface temperature to the imposition of an external forcing, e.g., anthropogenic CO 2 emis-R. Sussmann et al: The Zugspitze radiative closure experiment -Part 1 sions (Held and Soden, 2000). Finally, water vapor is a target species for spectrometric remote sensing methods based on the differential optical absorption principle, and, due to its high variability, it is also a potential interfering species for remote sensing of all other atmospheric trace gases (Frankenberg et al, 2008;Sussmann and Borsdorff, 2007;Sussmann et al, 2011). All in all, it is important to put efforts toward a quantitative understanding of all details of water vapor absorption throughout the whole terrestrial and solar infrared spectrum.…”

“…As part of the US Atmospheric Radiation Measurement (ARM) program (Ackermann and Stokes, 2003), a series of radiative closure experiments has been set up (e.g., Turner et al, 2004Turner et al, , 2012b which was complemented by the Italian ECOWAR (Earth COoling by WAter vapor Radiation) project (e.g., Bhawar et al, 2008;Bianchini et al, 2011). Various experiments have addressed the quality of (water vapor) line parameters in the FIR (Esposito et al, 2007;Delamere et al, 2010;Masiello et al, 2012), the water vapor continuum in the FIR (Tobin et al, 1999;Serio et al, 2008;Delamere et al, 2010;Liuzzi et al, 2014), and the water vapor continuum in the MIR (Turner et al, 2004;Rowe et al, 2006;Rowe and Walden, 2009). A crucial requirement for radiative closure experiments in the FIR and MIR is to select a site guaranteeing a wide range of IWV levels including the occurrence of very low IWV levels.…”

Spectrometric monitoring of atmospheric carbon tetrafluoride (CF<sub>4</sub>) above the Jungfraujoch station since 1989: evidence of continued increase but at a slowing rate

“…Line parameters adopted in the spectral fitting process were taken from the HITRAN 2004 spectroscopic compilation (Rothman et al, 2005), including the August 2006 updates (e.g., Esposito et al, 2007). For CF 4 , we selected a set of pseudo-lines whose intensities and temperature-dependent parameters were derived by one of us (G.C.T.)…”